Cap for a writing instrument



June 7, 1960 L. RoDENHAUsER ETAL 2,939,426

CAP FOR A WRITING INSTRUMENT Filed July 18. 1957 FIG. 2

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INVENTORS. [donf/ @asn/#4035,@- BYAI. ,Cefa wwf United States Pater CAP FOR A WRITING INSTRUMENT Ludwig Rodenhauser, 25 Alicestrasse, Oberramstadt, Germany, and Alfred Bauerle, 28 Darmstaedterstrasse, Oherramstadt, Hessen, Germany Filed July 18, 1957, Ser. No. 672,775

Claims priority, application Germany July 18, 1956 2 Claims. (Cl. 1Z0-42.01)

The invention relates to an improvement in caps for writing instruments, such as automatic pencils, ball point pens and fountain pens. Throughout the specification and claims, the term cap refers to closing caps which also serve to shift the plunger of the writing instrument and are located opposite the pen or the ball point end and those closing caps which enclose the pen point or the writing end of a ball point pen.

For the manufacture of this Vtype of cap it has been customary to use a malleable material, preferably Celluloid. The shells of the casings had to be so dimensioned that a thread cutting die could be inserted therein for cutting inner threads. As a result the expenses for material were relatively great and the work complicated. Celluloid has the additional disadvantage that the material shrinks and causes changes in the dimensions, which can make the caps useless.

According to the invention, the cap comprises a thinwalled outer shell of a malleable material which can be readily machined and an injection molded plastic lining which forms a unitary body with the shell. For purposes of firmly joining the shell with the lining, the shell may be provided with grooves, notches or protrusions for anchoring the lining in the shell in a manner well known per se.

In accordance with the invention, an open-ended thin sleeve is used to form the outer surface of the finished product. In the production method used up to now, the caps were shaped by turning and one was limited with respect to the shapes which could be produced. The tips of the caps had to be produced separately and glued or screwed on. These methods of joining tip and cap involved a special step in the work Iand the connected parts often became loose.

According to the invention, the outer cap shell Vmay be very thin `because it is not subjected to any mechanical strain. This is absorbed by a thick lining of injection molded material which carries the necessary threads for attaching the clip to the cap and for screwing the cap onto the shaft of the writing instrument. The conical tip is injection molded together with the lining and forms an integral part therewith.

The high pressure applied in the injection molding of the lining and tip assures a strong adherence of the 1ining to the outer shell to which it clings, producing a bond between the mushroom-like tip and the tapered end of the shell, the tip being flush with the outer surface of the shell and merging therewith without a Visible seam. This unitary cap body consisting of shell and lining can be accomplished only by injection molding `the lining.

The drawing illustratesV by way of example a cap for a fountain pen. In the drawing,

Fig. 1 is a longitudinal section of the pen with a cap for enclosing the pen-point and a screw cap for operating the ink supply plunger,

Fig. 2 is an exploded iview, partly in section, of the cap.

Referring now to the drawing, which illustrates an embodiment of the invention for purposes of illustration without limiting the invention thereto, there is shown a fountain pen shaft l with a cap enclosing the pen (not shown) and a screw cap for operating the plunger at the base of the shaft. The top cap includes a thin outer sleeve, for example of Celluloid, whose one end is conically tapered while a short meta-l sleeve or ring 3 is press tted in the non-conical end in such a manner that it protrudes therefrom. A decorative ring 4, for example of electro-oxidized aluminium, of iine metal or the like, is mounted over the protruding end of the metal ring 3 and is flush therewith.

The joining of cap and decorative ring can be effected by soldering or otherwise joining the two metal rings 3 and 4. 5 is the injection molded lining which supplements the shell 2 to produce the desired casing thickness and which is provided with the necessary shoulders, notches, threads, and the like, by use of a suitable molding die.

According to the illustrated embodiment, ythere is molded into the lining a screw socket l1 for receiving screw 6 holding the arm 7 of a clip S which is introduced through a slit l2. The screw cap on the lower endv of kthe pen is also formed from a conically tapered, open Celluloid sleeve 9. The injection molded lining, which supplements it vto the desired thickness and inner formation, is designated with 10.

We claim:

l. A cap construction for writing instruments, comprising a cap body of an outer shell with a conically tapered end having a central aperture, a metal ring fitted into the other end of the outer shell and protruding therefrom, and a plastic lining injection molded into the shell and extending from the metal ring through said opening and forming there a rounded mushroom-like tip closing the opening and ush with the outer surface of the outer shell whereby the mushroom-like tip is anchored to the tapered end of the shell, the tip having an axially extending tapped blind hole facing the other end.

l2. A cap construction for writing instruments, comprising a cap body of an outer shell with a conically tapered end having a central aperture, a metal ring itted into the other end of the outer shell and protruding therefrom, and a plastic lining injection molded into the shell and extending from the metal ring through said opening and forming there a rounded mushroom-like tip closing the opening and flush with the outer surface of the outer shell whereby the mushroom-like tip is anchored to the tapered end of the shell, the tip having an axially extending tapped blind hole facing the other end; a clip with an arm extending perpendicularly from said clip, the arm being mounted in a radially extending horizontal slot in the shell and the lining, the arm having a bore in alignment with the tapped blind hole and being adjacent thereto; and a screw extending through said bore into the tapped blind hole for attaching the clip to the cap body.

References Cited in the ile of this patent UNITED STATES PATENTS 1,872,064 Cuthbert Aug. 16, 1932 FOREIGN PATENTS 143,647 Great Britain .Tune 3, 1920 534,683 Great Britain Mar. 13, 1941 1,041,501 France May 27, 1953 

